An important hallmark of apoptosis and the subsequent clearance of apoptotic cells is that this process is non-inflammatory or 'immunological silent'. Moreover, the recognition and clearance of cells at their earliest stages of apoptosis is actively anti-inflammatory, and such post-engulfment response has been linked to generating and maintaining tolerance to self-antigens. Airway epithelial cells, which come in contact with the environment, are thought to undergo rapid turnover via different mechanisms of apoptosis. Yet, relatively little is known about how these apoptotic epithelial cells are cleared, the consequences of such clearance to normal lung biology, and whether defects in clearance mechanisms contribute to the secretion of anti- inflammatory mediators. We hypothesize that encounter with apoptotic epithelial cell results in TGF-p production from the engulfing cell. Such TGF-(3 would participate in the generation of Treg cells, which will limit inflammatory responses and provide a normal lung environment, which can be maintained by the routine epithelial cell turnover, with apoptotic cell clearance being mediated by the airway epithelial cells. Our long-term objective is to show the importance of epithelial cell clearance to lung homeostasis. In order to address this;(1) we will investigate the ability of primary airway epithelial cells to engulf apoptotic cells and secrete anti-inflammatory mediators after targeted knockdown of key engulfment molecules (ELM01 and Rad) via siRNA;(2) to test the importance of epithelial cell-mediated engulfment for the maintenance of healthy lung;(3) to determine the role of epithelial-mediated engulfment in the generation of regulatory T cells. We have engineered transgenic mice in which key engulfing molecules are conditionally deleted in the airways. These mice will be useful to study the role of engulfment to the maintenance of normal lung homeostasis. I have also developed an assay to measure the engulfment of apoptotic cells as well as an assay to measure the production of anti-inflammatory mediators. In addition, I am currently developing an assay that would analyze the differentiation of Treg cells in vitro. Every day millions of cells in the human body dye. The removal of dying cells is important for maintaining a healthy immune system. Otherwise, dying cells that are not efficiently removed may release toxic substances that are harmful to the human body. Cells that are in contact with the external environment, such as epithelial cells of the airways, may be critical for preventing disease. Understanding how dying cells in the airways are cleared will be beneficial for designing new strategies in the hope to prevent diseases characterized by chronic inflammation.